Air conditioning and refrigeration systems of all shapes and sizes are in common use throughout industry, commercial establishments, public buildings and residences. Such refrigerant compressor systems can be generally characterized as systems which circulate a compressor fluid containing lubricating oil and a refrigerant type of gas that is compressible into a liquid and which is then expanded for absorption of heat. Common refrigerants used at this time can be classified as CFC (chlorofluorocarbons), HCFC (hydrochlorofluorocarbons), HFC (hydrofluorocarbons), and HFO (hydrofluoroolefins). Under the CFC classification are R-11, R-12, R-13, R-13B1, R-114, R-500, R-502 and R-503. The HCFC classification includes R-22, R-123, R-124, R-401A, R-402A, R-402B, R-403B, R-408A, R-409A and R-414B. The HFC classification includes R-23, R-134a, R-404A, R407A, R-407C, R-R-410A, R-422B, R-422C, R-422D, R-507 and R-508B. The HFO classification includes HFO-1234yf. The lubricating oil can be mineral oil (highly refined naphthenic), polyol ester, alkyl benzene, polyalkylene glycol or polyalphaolefin. The particular oil is selected based on compatibility with the specific refrigerant utilized in the air-conditioning or refrigeration unit.
A major problem with air-conditioning or refrigeration systems is recurring compressor burnout. The term compressor burnout is used to describe a disabling electrical failure in the compressor's electric motor or related electrical components within the system. Burnout can occur from a variety of causes, including direct damage to the electrical coils of the motor or other electrical system components, or from strain on the motor arising from operating at too high a temperature, at the wrong pressure and/or with an incorrect electrical power supply. While several factors may be the cause of compressor burnout, one of the most common causes is the formation of acid in the compressor fluid.
The amount of acid in the lubricating oil is typically denoted by the total acid number (TAN). The total acid number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. It is an important quality measurement of a lubricating oil while in service. The TAN value can not only signify potential for burn-out but also help indicate the potential of corrosion problems.
Acids are generally formed in the compressor fluid by the presence of contaminants and moisture, or the breakdown of refrigerant, oil and/or degradation of system parts, neither of which processes can be completely avoided. The contaminants and moisture, along with system operating conditions tend to partially break down the chlorofluorocarbons comprising the compressor fluid, releasing free halogen ions. These ions then combine with moisture to form acids which subsequently attack internal system parts. A major factor in this acid attack is that the internal structure of the air-conditioning or refrigeration system generally comprises various different materials that are susceptible to acidic attack, including steel, copper and copper alloys, aluminum, various synthetic seals, terminals and insulators. Once acids have formed in the air-conditioning or refrigeration system, they can cause corrosion and deterioration of various system parts, forcing the compressor motor to work harder, causing direct damage to the compressor motor itself, or causing leaks to form which allow moisture to enter the system promoting further acid formation. Regardless of its source, the presence of acid can eventually result in compressor burnout.
Since corrosion is a result of acid attack, acid neutralizers also may be added to the lubricating oil. These are usually but not necessarily organic compounds. Such organic compounds may be, for example, carbodiimides, glycidyl ethers and epoxides, alkanolamines or arylamines (U.S. Pat. No. 6,235,687, incorporated herein by reference). A number of different compounds can be included in these particular classes of compounds (see for instance U.S. Pat. No. 3,346,496; U.S. Pat. No. 3,723,320, incorporated herein by reference). Another possible acid neutralizer is potassium hydroxide (KOH), added as an alcoholic solution (U.S. Pat. No. 5,503,757, incorporated herein by reference).
The neutralizing action of the KOH and other options can result in the formation of water. As discussed above, water can degrade the performance of air-conditioning or refrigeration systems in several ways, including increasing the rate of organic acid formation through hydrolytic reactions with synthetic oils. The use of hydrolytic drying agents such as orthoformates to completely remove water in HVAC systems has been suggested (WO2010028493, incorporated herein by reference).
When acid neutralizing agents such as alcoholates, carbodiimides, glycidyl ethers, epoxides, alkanolamines or arylamines react in refrigeration systems, the reactions occur in a non-aqueous medium. As a consequence, the reactions are not easily driven to completion but are said to be equilibrium controlled reactions. This can result in re-formation of the acid for a transient period of time and can result in the detrimental impacts discussed above.
There is a need in the art for a composition that can drive such equilibrium controlled reactions to completion through the removal of reaction products; and thus can help to ensure that acid is not re-formed. Moreover, there is a need in the art for a composition that can be used as an additive for neutralizing or removal of an acid in a refrigeration or air-conditioning system.